1. Field of the Invention
The present invention relates to a main circuit part of a vacuum circuit breaker, and more particularly, to a main circuit part of a vacuum circuit breaker with a temperature sensor.
2. Description of the Conventional Art
In general, a vacuum circuit breaker is a circuit breaker installed in a high voltage electric power system to break a circuit to protect the electric power system in the event of a dangerous situation such as a short circuit, an overcurrent, and the like, and it is designed by utilizing excellent insulating performance and arc-extinguishing capability in a vacuum state.
FIG. 1 is a side view illustrating a main body of a vacuum circuit breaker according to the conventional art. The main body 1 of the vacuum circuit breaker generally includes a main circuit part 2, an operation part 3, and a transfer part 4. Among them, the part essential for applying or cutting off a circuit voltage or current is the main circuit part 2.
As a large current flows in the main circuit part 2, heat is generated. The amount of heat generation is very large in the event of a fault current, and this may cause a problem with the normal operation of the breaker's main body 1 or damage to internal parts or load devices. To avoid situations like this, a temperature monitoring apparatus was developed to measure the temperature of the main circuit part 2.
As a prior art related to this type of apparatus, Korean Patent Registration No. 10-0883042 titled ‘Air Circuit Breaker with Temperature Sensor’ may be referred. This invention relates to an air circuit breaker with a temperature sensor which can monitor the temperature of the circuit breaker based on the current flowing in a conduction unit of the air circuit breaker. The air circuit breaker with a temperature sensor according to an exemplary embodiment of this invention includes a temperature sensor 150 which is inserted into a sensor insertion hole 115 formed in a base mold 110 and measures temperatures and a temperature indicator 160 which indicates the temperature of the current-carrying part with a measurement made by the temperature sensor 150.
In order to measure the amount of heat the main circuit part 2 of the conventional vacuum circuit breaker generates, as in the above prior art example, a temperature sensor 5 may be installed in the air to measure the upper-air temperature of the main body 1 where the main circuit part's heat is transferred via convection (case A), or a temperature sensor 6 may be configured to come into contact with a mold housing or insulator to indirectly measure the temperature of heat transferred (case B).
This is because a cable for power supply and a cable for data communication are necessarily connected to the temperature sensor 5 or 6. That is, a power cable is connected to the temperature sensor 5 or 6 to supply power, and a data cable is connected to the temperature sensor 5 or 6 to transmit data measured by the temperature sensor 5 or 6 to an external device. It is hard for these cables to bear high-temperature heat generated from the main circuit part 2. Also, forming various types of cables within the main body 1 in a complicated manner may cause a deterioration of insulation performance and bring disadvantages in terms of spatial design.
For this reason, a temperature sensor has been installed in proximity to the main circuit part 2 in the same way as shown in FIG. 1, which, however, decreases the accuracy of data measured by the temperature sensor installed in this way. This makes it difficult to accurately measure the temperature of the main circuit part 2 and gain practical benefits of monitoring. As a consequence, there still is a possibility that the main body 1 and peripheral equipment will get damage.
Moreover, the cable connected to the temperature sensor has to be pulled out to the front even when the temperature is installed directly on the main circuit part 2 to accurately measure the temperature of the main circuit part 2, which creates the possibility of insulation breakdown and failure due to the cable connected to the temperature sensor.